Adding Hydrated Lime in a Material Madeof Clayey Soil and Fibres: Formulationand Effects on Thermo-Mechanical Properties

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Résumé

In this study, we have focused our investigations on effect of adding hydratedlime on a locally made composite material, based on clayey earth (soil) andHibiscus sabdariffa fibres, for envelope (walls) in the building. Prior to sam-ple’s formulation, we selected an appropriate mineral (soil) material based oncriteria as: plasticizer power for good workability, dense coarse particles towithstand loads and finally porous structure to take advantage of air insulat-ing character. We then formulated, following a mixing process by shearingand compaction by vibration that we recommend, two composite materials(A), (B) which contain respectively 1% Fibres plus 1% lime, 1% Fibres plus3% lime. We determined thermal properties by the mean of KD2 Pro thermalanalyzer, compression strength accordingly to the standard NF P 18-406, po-rosity following volumetric and gravimetric methods and pH of soil-hydratedlime solution. As results, up to 5% of hydrated lime, the measured pH is infe-rior to 12: mineralization of vegetal fibres is highly unlikely. Moreover, weobserve that the addition of hydrated lime resulted in a reduction in thenumber of cracks and their depths; Samples (A) and (B) have a rather com-pact appearance than the case 1% Fibres without lime (material (C)). Fur-thermore, with lime stabilization, the insulating potential is improved whilethe thermal inertia has been deteriorated compared to material (C). However,compressive strength decreases with lime, which could be due to the presenceof fibres that would inhibit the hardening of the lime. At last, with 3.39% ±3.07% MPa, 2.27% ± 11.30% MPa for samples (A), (B) respectively, the min-imum required by CRATerre-EAG (guide of CDI, 1996) for construction ofenvelope (walls) of single storey (ground floor) buildings is met.

Mots-clés

Local Material, Hydrated Lime, Hibiscus sabdariffa Fibre, Thermo-Mechanical Properties, Porosity